1. Field of the Invention
The present invention relates generally to compensation devices and methods for fluidic oscillation flow meters and, more particularly, to a compensation device and method for a fluidic oscillation flow meter which compensates both for inconsistencies in the measured values due to the characteristics of the fluidic oscillation flow meter used to measure a flow rate of fluid and for inconsistencies in the measured values attributable to the deformation of a mold which may be induced when conducting an injection molding process to produce a fluidic oscillator used to implement fluidic oscillation.
2. Description of the Related Art
With regard to flow meters using oscillation of fluid jets to measure flow rates, fluid discharged from a jet drops in pressure when it comes out of the outlet of the jet. Due to the dropped pressure, the fluid is attracted to a nearby surface and flows along the surface. This phenomenon is called the “Coanda effect”.
If a path is provided for the fluid such that some of the fluid which flows along the nearby surface because of the Coanda effect is guided along the fluid path towards the outlet of the jet, the fluid thus flowing along the nearby surface collides with fluid which is flowing forwards thereby impeding advancement of the discharged fluid. Thereby, the fluid jet oscillates. A period of the oscillating fluid jet is proportional to the flow rate of fluid. Hence, the flow rate of the fluid can be determined using the ratio of it to the period. This principle is called “fluidic oscillation”. A structure manufactured using the fluidic oscillation principle is called a “fluidic oscillator”.
The fluidic oscillator includes a jet nozzle which forcibly discharges fluid, a feedback channel through which discharged fluid reduced in pressure flows towards the jet nozzle along the nearby surface due to the Coanda effect, and an obstacle which promotes oscillations in the discharged fluid.
To analyze the period of oscillation of fluid with respect to the flow rate, the fluid must have a regular laminar flow. Reynolds number analysis is used to discern whether the flow of fluid is in the regular state or not. A boundary value at which the flow of fluid changes from laminar to turbulent is called the “critical Reynolds number”. Even though a fluidic oscillator should be designed such that the laminar flow of fluid is stably maintained, a fluidic oscillator which is over the critical value may be manufactured depending on conditions (pressure, temperature, humidity, etc.) present during the injection molding process. In this case, there is a problem because despite the fluid passing through the fluidic oscillator at the same flow rate, the results may differ.
Furthermore, because of some characteristics of the flow meter using the above-mentioned fluidic oscillation, when the flow rate of fluid passing through the flow meter linearly varies, oscillation frequency of the fluid is also changed depending on variations in the flow rate. Thus, the measured data is detected as non-linear rather than having a constant proportional value.
Therefore, a fluidic oscillation flow meter and a method are required, which are capable of correctly measuring the flow rate of fluid despite the problem induced by the characteristics of the fluidic oscillator which may be over the critical value and despite variations in oscillation frequency of fluid depending on variations in the flow rate.